Can two gas fireplaces share the same chimney?

If you are undergoing home renovations, you may be asking, can two gas fireplaces share the same chimney? Perhaps you would like a fireplace in both your living room and dining room, but you only have one chimney… Having two gas fireplaces share the same chimney can be very convenient. However, having a shared chimney can create unforeseen health hazards if not properly planned. Keep reading for information about whether or not this is an option.

What you need to know: chimneys and flues

Within a fireplace, the flue is a duct or pipe situated inside the chimney, providing a sealed pathway from the gas fire to the outside of a building. For gas fires, a metal flue is most commonly used. A chimney can have multiple flues, with each flue venting a gas appliance, fireplace, or other device. It’s important that the chimney is properly constructed to ensure the necessary spacing and sealant between the individual flues.

Flues are lined with fire-resistant material on the inside, which is typically refractory concrete or impervious clay, but may sometimes be metal. All chimneys are required to be built with a flue lining, as this protects the masonry from combustion gases. The flue lining also improves the flow of the gases.

The damper is a pivoted or sliding metal flap in the flue, regulating the amount of draught and preventing excessive variations in airflow. It can also prevent heat loss, by closing off the interior of your home from the outside world.

Flues for gas fireplaces: the details

Most gas fireplaces use a balanced flue that goes through the wall, just like a gas boiler. Another option is to use a powered flue, which allows the exhaust gas to be carried over longer routes with bends. Powered flues allow you more freedom as to where you place your gas fire, as they no longer have to be located near an external wall.

A powered flue draws in clean air and expels any waste gases using an external pipe; they are fitted with a fan to prevent overheating. As a powered flue can allow you to have fireplaces on any wall in your home, this often means that people have more than one fireplace, ensuring that cosy feeling throughout their property.

Sharing a chimney

Shared chimney flues mean that the flue that expels any waste gases must be shared between two fireplaces. If the construction is not done properly there is a danger of a fire spread, combustion gas, or carbon monoxide hazards. As a rule of thumb, each appliance that produces combustion gases needs to have its own dedicated flue to vent combustion gases safely out of the building. If this is not the case, dangerous gases may be inadvertently conducted from one area of the building to another.

It is common for a single flue to serve both a heating appliance, such as a boiler or water heater, and a fireplace. But the question is, can two fireplaces share one chimney?

Can two gas fireplaces share the same chimney flue?

Two gas appliances, such as a water heater and heating boiler, may be vented into the same chimney flue if your local authority approves of this installation. This means that in theory, two gas fireplaces should be able to use the same chimney, but you will need to ensure with your local authority that it won’t pose a danger to your home.

If the gas appliances are on separate floors, there is a potential increased risk of fire or gas leaks between floors. Depending on the particular circumstances, additional installation requirements may be imposed, or sharing the same chimney flue may not be permitted. This is something to enquire about with your local authority.

If the chimney is an older (typically clay-lined or with masonry construction), venting gas-fired heating equipment into it may be unsafe. The lower exhaust gas temperatures produced by gas-fired appliances may result in an inadequate draught, and risk fatal carbon monoxide poisoning of the building occupants. Before proceeding, it is advisable to seek the advice of your local fire officials and your local building control officer. This will ensure that your building is safe, allowing you to use your fireplaces with peace of mind.

If you are looking for advice regarding your gas fireplaces, or you would like to enquire about alternative fireplace types, such as a wood burner or an electric fireplace, get in touch with us. Our team at Fiveways Fires & Stoves are experts in providing fireplace services. Just give us a call on 0208 127 4747 or email .